Digital signal compression (sometimes referred to as video coding or video encoding) is widely used in many multimedia applications and devices. Digital signal compression using a coder/decoder (codec) allows streaming media, such as audio or video signals to be transmitted over the Internet or stored on compact discs. A number of different standards of digital video compression have emerged, including H.261, H.263; DV; MPEG-1, MPEG-2, MPEG-4, VC1; and AVC (H.264). These standards, as well as other video compression technologies, seek to efficiently represent a video frame picture by eliminating the spatial and temporal redundancies in the picture and among successive pictures. Through the use of such compression standards, video contents can be carried in highly compressed video bit streams, and thus efficiently stored in disks or transmitted over networks.
MPEG-4 AVC (Advanced Video Coding), also known as H.264, is a video compression standard that offers significantly greater compression than its predecessors. The H.264 standard is expected to offer up to twice the compression of the earlier MPEG-2 standard. The H.264 standard is also expected to offer improvements in perceptual quality. As a result, more and more video content is being delivered in the form of AVC (H.264)—coded streams. Two rival DVD formats, the HD-DVD format and the Blu-Ray Disc format support H.264/AVC High Profile decoding as a mandatory player feature. AVC (H.264) coding is described in detail in “Recommendation ITU-T H.264, Series H: AUDIOVISUAL AND MULTIMEDIA SYSTEMS Infrastructure of audiovisual services—Coding of moving video, “Advanced video coding for generic audiovisual services”, International Telecommunication Union, Telecommunication Standardization Sector, Geneva, Switzerland, January, 2012, the entire contents of which are incorporated herein by reference for all purposes.
Video encoding can be done on a general purpose computer in software or may be done with specialized hardware referred to as a hardware video encoder. Use of a hardware video encoder is regarded as key to achieving high performance video compression with low system resource usage.
A hardware decoder accelerator is a system resource shared by multiple users. Typically, the accelerator has higher than normal process privilege to access user's private memory, system registers and sometimes kernel memory. This makes the accelerator a possible target for security attacks.
It is within this context that aspects of the present disclosure arise.